For example, when an omnidirectional acoustic field is replayed by a Higher Order Ambisonics (HOA) using an annular or spheral speaker array, an area (hereinafter, referred to as a reproduction area) in which a desired acoustic field is correctly-reproduced is limited to the vicinity of the center of the speaker array. Thus, the number of people that can simultaneously hear a correctly-reproduced acoustic field is limited to a small number.
In addition, in a case where omnidirectional content is replayed, a listener is considered to enjoy the content while rotating his or her head. Nevertheless, in such a case, when a reproduction area has a size similar to that of a human head, a head of a listener may go out of the reproduction area, and expected experience may fail to be obtained.
Furthermore, if a listener can hear a sound of the content while performing translation (movement) in addition to the rotation of the head, the listener can sense feeling of localization of a sound image more, and can experience a realistic acoustic field. Nevertheless, also in such a case, when a head portion position of the listener deviates from the vicinity of the center of the speaker array, realistic feeling may be impaired.
In view of the foregoing, there is proposed a technology of moving a reproduction area of an acoustic field in accordance with a position of a listener, on the inside of an annular or spheral speaker array (for example, refer to Non-Patent Literature 1). If the reproduction area is moved in accordance with the movement of a head portion of the listener using this technology, the listener can always experience a correctly-reproduced acoustic field.